Glyphosate behavior at soil and mineral-water interfaces

Area of Science:

• Environmental Chemistry
• Soil Science
• Surface Chemistry

Background:

• Glyphosate (PMG) is a widely used herbicide.
• Understanding its adsorption in soils is crucial for environmental risk assessment.
• Soil mineralogy and pH significantly influence pesticide-herbicide interactions.

Purpose of the Study:

• To quantify glyphosate (PMG) adsorption on Argentine soils with varying mineralogical compositions.
• To investigate the effect of pH and soil properties on PMG adsorption.
• To model PMG adsorption using Langmuir isotherms and determine surface coverage.

Main Methods:

• Adsorption isotherms and zeta potential measurements for PMG/soil systems.
• Analysis of three Argentine soils with different mineralogical compositions.
• Application of Langmuir isotherms to model adsorption and estimate surface coverage.

Main Results:

• PMG adsorption was successfully described by Langmuir isotherms.
• Montmorillonite and soil surfaces exhibited negative charges that increased with PMG adsorption.
• Surface coverage of PMG decreased with lower organic matter and iron content in soils and minerals.

Conclusions:

• Soil mineralogy, pH, organic matter, and iron content are key factors governing glyphosate (PMG) adsorption.
• Adsorption mechanisms involve surface complexation, leading to more negative surface charges.
• These findings are vital for predicting PMG mobility and persistence in agricultural soils.